I have a question about the thermactor pump and the valve. I have a 70 Mark III. What is the purpose of it? I know it has something to do with early emissions. If the pump or valve is bad or going bad what are the symptoms? The reason for the question is my car developed a low roar/humming noise in idle and park mode not noticeable at high speeds. This noise is very annoying I checked all exhaust pipes retightened all bolts on exhaust. It does not sound like a exhaust pipe leak at all but I wanted to rule it out. I have vacuum everything works on vac side of car and does not sound like vac leak either. So the only other thought was this pump/valve? I talked to a older gentlemen who said when the valve went bad it blew out his mufflers on a 71 mark. Can you shed some insight on this bewildering noise? Thanks in advance.
Hi Phil –
You are correct, that system is an early attempt to clean up excess tail pipe emissions during the early years of federal gov’t pressures concerning automobile pollution. During those years the manufacturers were dealing with different fuels and engine designs and it would be difficult to know how effective these early devices are now with the low quality fuels of today containing ethanol.
Without actually being able to hear these engine noises that you are concerned with it would be difficult to advise you if they are caused by the thermactor unit on your Mark III or not. If you do however suspect the pump you could remove the drive belt to the pump and operate the car normally in order to possibly eliminate or prove the pump as the cause. Many owners have successfully removed this pump along with all of the pipes and valves etc. on these collector cars with no problems whatsoever with performance or local gov’t inspections.
When diagnosing annoying sounds such as you are describing keep in mind that the cause could be as simple as a loose or cracked engine accessory bracket etc. Your description of “low roar and humming” suggests to me a cooling fan thermal clutch that has possibly “locked up” causing the radiator cooling fan to operate in the full ENGAGED mode at all times. Let us know what you find and we will post the results.